The justification for the Government’s proposed carbon tax and the recently reported expenditure of $5.5 billion on combating man-made global warming (AGW) is based on the official temperature record.

The official temperature record is produced by the Australian Bureau of Meteorology (BoM). The BoM produces the temperature record by adjusting the raw temperature data so that temperature trends can be seen. The BoM temperature record shows an increasing temperature trend over the 20th century.

The method of adjusting the raw data by BoM is similar to the method used in New Zealand. In New Zealand the temperature record is produced by the National Institute for Water and Atmospheric Research (NIWA). Recently a group of scientists has taken legal action against NIWA for improper manipulation of the temperature record. The New Zealand Climate Science Coalition found that NIWA had adjusted raw data which showed only a slight increase of 0.006 degrees Centigrade to an increase of 0.9 degrees. In effect no increase at all had been manipulated to show an increase consistent with AGW.
The Defence of NIWA was to disavow its own temperature record and to call in BoM to appraise its methods.

In its appraisal of NIWA released in December 2010, BoM did not examine the raw temperature data used by NIWA or how that data had been compiled. According to Neil Plummer, acting assistant director of BoM’s Climate Information Services what the BoM review did was merely appraise the methods of adjustment or “homogeneity corrections” used by NIWA.

Since the methods of homogeneity corrections used by NIWA are similar to those used by BoM it was no surprise that BoM found no fault with them.

But at no time did BoM consider whether the raw data was sufficiently faulty so as to justify the homogeneity corrections.

The involvement of BoM in the New Zealand dispute is problematic because a formal request has been made to the Australian Auditor General to audit BoM’s official Australian temperature record and the methods used by BoM to adjust the Australian raw temperature data.

Researchers have found that BoM has adjusted the raw data upwards by 40 per cent for rural temperatures and by 70 per cent for the urban temperatures. This means that a temperature trend of 0.6 degrees for rural locations was increased to 0.85 degrees while in the towns and cities the trend of 0.4 degrees was increased to 0.78 degrees.

The reasons for these adjustments which involve changing well-established data from the beginning of the 20th century and also more recent data has been provided by BoM in a 2003 paper by BoM scientists, Della-Marta, Collins and Braganza. The five criteria for BoM’s adjustments of the raw data include missing data and various “suspected” defects in the temperature recording process and equipment. However, in Dell-Marta et al’s paper only those sites which have been removed from the official record have criteria noted. Those sites still included and which have been adjusted have no indication as to why they have been adjusted. The odd thing is that the older data is usually adjusted by making it cooler while the modern data is usually adjusted to make it warmer. This has the automatic effect of increasing the temperature trend.

When researcher Ken Stewart sought an explanation from BoM he was informed by Dr David Jones, the head of Climate Monitoring and Prediction, National Climate Centre that:

“On the issue of adjustments you find that these have a near zero impact on the all Australian temperature because these tend to be equally positive and negative across the network.”

The Application for an audit of the BoM adjusted temperature record argues that what Dr Jones has claimed is clearly not the case; the Application shows that the BoM adjustments have produced a temperature record which is consistent with AGW and that the raw data showed a temperature record which was not consistent with AGW.

The Australian and New Zealand official temperature records are not the only ones being disputed or at least analysed. A team led by Berkeley Professor of physics, Richard Muller, is in the process of analysing 1.5 billion bits of raw climate data. The project is called The Berkeley Earth Project and will examine the temperature data used by NASA's Goddard Institute for Space Studies, the National Oceanic and Atmospheric Administration (NOAA), and the MET Office in England. These climate Institutes are the sources of the global official temperature records used by the Intergovernmental Panel for Climate Change (IPCC).

The motivation for The Berkeley Earth Project is in part because, as Muller says, the temperature data that is used by NASA, NOAA and the MET is filtered (that is adjusted) and might not be as representative as it could be.

Given these developments the Australian government should not bring in a carbon tax or continue spending vast amounts of money on AGW until the audit of the BoM record, at the very least, is completed. If the official temperature records are incorrect then great doubt will be cast on the main proof for AGW. If AGW either does not exist or has been exaggerated then a carbon tax will not be a solution but just another great big tax.